Torsional vibration damper

ABSTRACT

The invention relates to a torsional vibration damper comprising a hub member, an inertia member comprising at least two parts and being disposed about a peripheral portion of the hub member to define a cavity and a viscous fluid disposed in said cavity, each of said two parts of the inertia member being cut away in a region adjacent the hub member, and an elastic tuning element formed from a high resilience, low hysteresis material located in each said cut away portion in such manner that each said elastic element is under both axial and radial compressive stress to locate positively said inertia member both axially and radially relative to said hub member, and also acts as a seal between said hub member and said inertia member whereby to seal said viscous fluid in said cavity.

United States Patent [191 Hall [54] TORSIONAL VIBRATION DAMPER [75]Inventor: Jeffrey Hall, Huddersfield, England [73] Assignee: HoudailleIndustries Inc., Buffalo,

[22] Filed: Apr. 2, 1971 [21] Appl. No.: 130,736

521 U.S.Cl .Q ..267/l37,267/l29 51 lnt.Cl ..Fl6k 7/00 [58] FieldofSearch..267/l29,l37,l36

Primary ExaminerJames B. Marbert Att0rneyDiller, Brown, Ramik & Holt 1May 22, 1973 [57] ABSTRACT The invention relates to a torsionalvibration damper comprising a hub member, an inertia member comprisingat least two parts and being disposed about a peripheral portion of thehub member to define a cavity and a viscous fluid disposed in saidcavity, each of said two parts of the inertia member being cut away in aregion adjacent the hub member, and an elastic tuning element formedfrom a high resilience, low hysteresis material located in each said cutaway portion in such manner that each said elastic element is under bothaxial and radial compressive stress to locate positively said inertiamember both axially and radially relative to said hub member, and alsoacts as a seal between said hub member and said inertia member wherebyto seal said viscous fluid in said cavity.

6 Claims, 8 Drawing Figures PATENTEDMRYEZIW 3,734,484

SHEET '1 0F 2 INVENTORZ AEFFREY W ATTOENEYS 'PATENTEDHAYZZIW 3.734.484

' SHEET 2 BF 2 INYENTOR:

JEFFREY HALL I ATTORNEYS TORSIONAL VIBRATION DAMPER The presentinvention relates to torsional vibration dampers of the type intended,for example, to be mounted on the end of the crankshaft of areciprocating engine, such as an internal combustion engine.

Two types of torsional vibration dampers are in common use, the tunedrubber damper and the untuned viscous damper. The usual form of tunedrubber damper consists of an inertia mass coupled to a hub member bymeans of a rubber or other elastomeric element. The hub member isrigidly attached to the engine crankshaft. In operation the damperintroduces a second mode of vibration into the system, by using theelastic properties of the rubber element as a tuning spring. The peakamplitudes of the two modes of vibration thus produced are reduced bythe damping effect of the internal hysteresis of the rubber elementconverting the vibration energy to heat. The rubber thus performs thetwo functions of tuning and damping. The tuned damper of this type isadvantageous in that under resonant conditions the tuned inertia massvibrates at greater amplitudes than the input vibrations and the energyrequired for the damping function may be obtained from a relativelysmall inertia mass compared with the inertia mass of an untuned damperdesigned for the same system. A major disadvantage of the tuned damperincorporating rubber or elastomeric materials with high internalhysteresis values is the poor thermal conductivity of such materialswhich causes a build up of heat within the rubber element andconsequently results in high working temperatures. These high workingtemperatures define the operational limits of such dampers to therelatively low input, energy level which generates the temperaturewithin the tuning element at which it begins to lose its desiredproperties.

The untuned viscous damper consists of an inertia mass coupled to ahousing by means of a thin film of a high viscosity liquid and thehousing is rigidly attached to the engine crankshaft. The vibrationamplitudes of the system are reduced by the vibration energy beingabsorbed and converted to heat in shearing the film of liquid betweenthe inertia mass and housing.

The heat generated is readily dissipated to atmosphere from the largesurface area of the housing. Because the inertia mass in this device isuntuned its amplitude is always less than the input amplitude and itmust be of relatively large mass compared with the inertia mass of atuned damper.

According to the present invention there is provided a torsionalvibration damper comprising a hub member, an inertia member comprisingat least two parts disposed about a peripheral portion of the hub memberto define a cavity accommodating said peripheral portion and containinga viscous fluid, each of said two parts of the inertia member being cutaway in a region adjacent the hub member, and an elastic tuning elementformed from a high resilience, low hysteresis material located in eachsaid cut away portion in such manner that each said elastic element isunder both axial and radial compressive stress to locate positively saidinertia member relative to said hub member, both axially and radiallyand also acts as a seal between said hub member and said inertia memberto seal said viscous fluid in said cavity.

The present invention thus provides a torsional vibration damper withrubber or elastomeric spring tuned and viscous damped inertia mass. Theuse of low internal hysteresis materials permits the dampers to accepthigher levels of vibration energy before the build up of heat in thetuning element creates a working temperature at which the tuning elementloses its desired properties. A further advantage is achieved becausethe tuned inertia mass vibrates at higher amplitudes than the inputamplitude and the viscous damping action may thus be more effectivelyused with the smaller inertia mass usually associated with tuned dampersthan with normal viscous dampers. Still further advantages may lie inthe construction of the present damper in that manufacture and assemblymay be relatively simple, and may be of low cost.

The elastic elements provide positive radial location of the inertiamember by opposed compressive stresses and positive axial location byopposed compressive stresses.

Any viscous fluid may be used in the fluid chamber and the viscosity ofthe fluid selected will depend upon the use to which the damper is to beput. It is however envisaged that for most purposes a silicone fluidhaving a viscosity of up to 1 million centistokes will be used.

The materials selected for construction of the damper should be suchthat the damping fluid and the elastic tuning elements and hub andinertia members are inert to one another.

The preferred material from which the tuning elements are made isnatural rubber although other high resilience, low hysteresis materials(generally elastomers) may be suitable. Natural rubber and some of theother elastomers however, suffer from the disadvantage that they areincompatible with silicone fluids.

This is evidence by a severe loss of viscosity of the silicone fluidwhen the combination is subjected to heat such as is developed duringoperation of the damper.

Although the construction of the damper of the invention is such thatthe area of tuning element exposed to the silicone fluid is relativelysmall, it is advisable, when using elastic elements made from materialswhich are incompatible with the fluid being used, to provide at leastthose parts of the elastic elements which will be in contact with thefluid (and preferably the whole surface) with an outer surface layer ofa material inert to the fluid, e.g. chemically inert synthetic rubber.The coating may be of the order of 0.005 inches thick.

The elastic elements in addition to acting as tuning elements also serveto locate the hub and inertia members relative to each other bothaxially and radially and act as seals to prevent egress of viscous fluidfrom the drive chamber. By locating the hub member and inertia mass bothaxially and radially accurate control of the clearances between the hubmember and inertia mass may be achieved.

If desired, the tuning elements may be bonded in position though this isnot essential for location or sealing purposes.

If desired, the inertia member may be formed with a V cross-sectiongroove so that the inertia member may serve as a pulley. The inertia ofthe pulley is thus not added to the hub inertia.

Where the inertia member is designed to be used as a pulley it ispreferred that the tuning elements are bonded in position to withstandthe additional superimposed torsional load of the driven accessory.

The invention will now be further described by way of example withreference to the accompanying draw- 3 ings of which all of the FIGS. (1to 8) show sectional views through various examples of dampersconstructed in accordance with the present invention. In each case onlyhalf of the damper is shown, as the dampers are symmetrical. Throughoutthe description of the drawings, like reference numerals have been usedto refer to similar parts.

Referring firstly to FIG. 1, the damper shown includes a hub member,indicated generally by the reference numeral 10, comprising a centralannular portion 12 having an integrally formed annular flange 14extending from the periphery of the central portion 12 at right anglesthereto. A radially extending flange 16 is formed integrally with theflange 14. An inertia member comprising two parts 18 and 20 is disposedabout the flange portion 16 in concentric relationship with the hubmember 10. The two parts 18,20 of the inertia mass are connected onewith another by a lip portion 22 formed on one of the inertia parts 18which is rolled over a flange portion 24 formed on the other part 20 ofthe inertia member to enclose a synthetic resin seal 23. (Alternativelythe lip portion 22 may be rolled over and welded to the flange portion24). The two parts of the inertia member together from a cavity 25 inwhich a peripheral portion 16 of the hub member is accommodated. Each ofthe two parts 18,20 of the inertia member is cut away at 26,28respectively in a region adjacent the angle formed between flanges 14and 16. Elastic tuning elements 30,32 (which are O-rings when not undercompression) are disposed in the cut away portions. The elastic elementsare under axial and radial compressive stress and locate the inertiamember both axially and radially relative to the hub member and alsoserve to seal the drive chamber 25. Viscous fluid may be introduced tothe drive chamber 25 through opening 34 before the cap 36 is fixed inplace. In operation the elastic elements 30,32 act in three ways.Firstly, they act as tuning elements, secondly they act to radially andaxially locate the hub and inertia members relative to one another andthirdly they act to seal the drive chamber 25. It can be seen from FIG.1 that the area of contact between the fluid in the drive chamber 25 andthe elastic elements is small.

Where the elastic elements are however made from a material which is notinert with respect to the viscous fluid, at least that part of theelements which will be in contact with the fluid (and preferably all ofthe surface of the elastic elements) is provided with an outer surfacelayer of a material which is inert with respect to the fluid, e.g. achemically inert synthetic rubber.

The damper shown in FIG. 2 is of similar construction to the damper ofFIG. 1 with the exception that the two parts 18,20 of the inertia memberare connected by rivets 38 (or bolts) which extend through the damperunit. To allow a certain amount of relative movement between the inertiamember and the hub member, such as is necessary in a damping device,holes 40 in the flange 16 are oversize.

This arrangement is generally more suitable when the two parts 18, ofthe inertia member are made from cast iron.

The damper of FIG. 3 is similar to that of FIG. 1 with the exceptionthat the hub member 10 is constructed from two parts 42,44 whichtogether form a hub member of a shape similar to that of FIG. 1.

The arrangement shown in FIG. 4 is similar to that of FIG. 1 with theexception that the hub member 10 is made up from three parts 46,48 and50. These three parts combine to form a hub member of a shape similar tothat of FIG. 1 with the exception that the central portion 12 isdisposed in a' position symmetrical with respect to the flange 14.

FIG. 5 shows the damper of FIG. 1 modified by the incorporation of a Vcross-section channel 52 so that the inertia member may act as a pulley.

In the arrangement shown in FIG. 6 the hub member comprises four annularparts 54,56,58, 60 the inner two 56/58 of which are bent over at rightangles to the periphery of the hub member 10 to form flanges 62,64.These flanges are located in correspondingly shaped annular groovesformed in the two parts 18, 20 of the inertia member. This arrangementincreases the area of the hub member and inertia member which is inshear relationship.

In the arrangement shown in FIG. 7 the flange 14 is omitted and theinertia members 18,20 are cut away (at 26,28) in the region adjacent theflanges 62,64. The elastic tuning elements 30,32 are located in thecutaway portions 26,28 as in the previous embodiments described.

The arrangement shown in FIG. 8 is similar to that of FIG. 1 with theexception that the junction between flanges l4 and 16 is shaped at 66,68so that the compressed elastic elements 30,32 will have parallel orsubstantially parallel surfaces 70,72 and 74,76 with part of the elasticelements accommodated in the gap between the flange l4 and the inertiamember. The radial thickness of each element may thus be uniform orsubstantially uniform throughout its length and may be thinner than inconstructions 1 to 7. When constructed in this manner the stiffness ofthe coupling between the hub 10 and the inertia mass 18,20 may beincreased. The outer portion (not shown) of the damper of FIG. 8 may besimilar to the outer portion of the damper shown in any one of FIGS. 1to 7.

In FIG. 8 the elastic elements when in the free uncompressed state neednot be in the form of O-rings. In FIGS. 1 to 7 the elastic elements aregenerally such that in this free uncompressed state they are in the formof O-rings.

I claim:

1. A torsional vibration damper comprising a hub member, an inertiamember comprising at least two parts and being disposed about aperipheral portion of the hub member to define a cavity and a viscousfluid disposed in said cavity, each of said two parts of the inertiamember being cut away in a region adjacent the hub member, and anelastic tuning element formed from a high resilience, low hysteresismaterial located in each said cut away portion in such manner that eachsaid elastic element is under both axial and radial compressive stressto locate positively said inertia member both axially and radiallyrelative to said hub member, and also acts as a seal between said hubmember and said inertia member whereby to seal said viscous fluid insaid cavity.

2. A damper according to claim 1, wherein said cavity contains asilicone fluid having a viscosity of up to 1 million centistokes.

3. A damper according to claim 1, wherein the tuning elements comprise anatural rubber having an outer 3 ,7 3 4 ,4 8 4 5 6 surface layer of asynthetic rubber which is chemically member is formed with a Vcross-section groove so that inert to the damping fluid. the inertiamember may serve as a pulley.

4. A damper according to claim 3, wherein the outer 6. A damperaccording to claim 5, wherein the tuning surface is approximately 0.005inches thick. elements are bonded in position.

5. A damper according to claim 1, wherein the inertia 5

1. A torsional vibration damper comprising a hub member, an inertiamember comprising at least two parts and being disposed about aperipheral portion of the hub member to define a cavity and a viscousfluid disposed in said cavity, each of said two parts of the inertiamember being cut away in a region adjacent the hub member, and anelastic tuning element formed from a high resilience, low hysteresismaterial located in each said cut away portion in such manner that eachsaid elastic element is under both axial and radial compressive stressto locate positively said inertia member both axially and radiallyrelative to said hub member, and also acts as a seal between said hubmember and said inertia member whereby to seal said viscous fluid insaid cavity.
 2. A damper according to claim 1, wherein said cavitycontains a silicone fluid having a viscosity of up to 1 millioncentistokes.
 3. A damper according to claim 1, wherein the tuningelements comprise a natural rubber having an outer surface layer of asynthetic rubber which is chemically inert to the damping fluid.
 4. Adamper according to claim 3, wherein the outer surface is approximately0.005 inches thick.
 5. A damper according to claim 1, wherein theinertia member is formed with a V cross-section groove so that theinertia member may serve as a pulley.
 6. A damper according to claim 5,wherein the tuning elements are bonded in position.